In co-pending application Ser. No. 07/510,699 filed Apr. 18, 1990, entitled SILICON SUBSTRATE HAVING AN EPITAXIAL SUPERCONDUCTING LAYER THEREON AND METHOD OF MAKING SAME, there is described a process for growing epitaxial thin films of high temperature superconducting oxide, yttrium, barium and copper oxide materials, for example YBCO, on a silicon substrate using an intermediate layer of cubic zirconia. Because of their epitaxial nature, these thin films have properties that are far superior to previous work on silicon and are comparable to single crystal in the best YBCO films grown on other substrates. Reproducible films with critical current densities 2.times.10.sup.6 A/cm.sup.2 at 77.degree. K. are described. Their noise levels are extremely low and well suited to bolometers. Epitaxy is critically important to obtain high quality films due to the degradation of the electrical properties across randomly aligned grain boundaries. Control of the epitaxy and the proper preparation of the silicon surface are disclosed in said co-pending application, which is incorporated herein by reference.
The growth of insulating epitaxial oxides on Si is an expanding research topic with important technological applications. Epitaxy refers to the crystalline alignment of a thin film material with its substrate, which may be a different material with a different crystal structure. The possibilities typically cited for work on insulating layers on Si include metal-insulator-semiconductor structures and three-dimensional integrated circuits. The present invention is directed more specifically to a buffer layer for the growth of high temperature superconductor layers or films on silicon substrates. It is also desirable to provide epitaxially grown insulating films or layers which can etched by wet chemicals such as hydrofluoric acid contrasted to buffer films which must be removed by ion milling, plasma etching, or laser ablation.